IV HAT IS A FERN ? 
103 
manner — that is to say, from the top of the frond 
spirally downwards. In the simple fronds there is 
one simple unrolling from the base outwards to the 
extreme uppermost point of the frond. In the 
compound species of the plant there is first of all 
the primary unrolling, and that is followed when 
completed by the lateral unrolling of the leaves on 
the rachis, which lateral unrolling is followed by 
perpendicular and lateral unrolling in alternation. 
